spline.c (1351B)
1 /* 2 Produce spline (uniform knots, second order) 3 from guiding points 4 */ 5 #include "mplot.h" 6 void splin(int mode, int num[], double *ff[]){ 7 int i, *np, n; 8 double xa, ya, xc, yc, *xp, *yp, *xp0, *yp0, *xpe, *ype; 9 double **fp; 10 np = num; 11 fp = ff; 12 while((n = *np++)){ 13 xp = *fp++; 14 yp = xp + 1; 15 xp0 = xp; 16 yp0 = yp; 17 xpe = xp0 + 2 * (n - 1); 18 ype = yp0 + 2 * (n - 1); 19 if (n < 3) { 20 plotline(*xp, *yp, *(xp + 2), *(yp + 2)); 21 continue; 22 } 23 if (mode == 4) { /*closed curve*/ 24 xa = 0.5 * (*xpe + *(xpe - 2)); 25 xc = 0.5 * (*xpe + *xp0); 26 ya = 0.5 * (*ype + *(ype - 2)); 27 yc = 0.5 * (*ype + *yp0); 28 parabola(xa, ya, xc, yc, *xpe, *ype); 29 xa = 0.5 * (*xpe + *xp0); 30 xc = 0.5 * (*(xp0 + 2) + *xp0); 31 ya = 0.5 * (*ype + *yp0); 32 yc = 0.5 * (*(yp0 + 2) + *yp0); 33 parabola(xa, ya, xc, yc, *xp0, *yp0); 34 } 35 else { /*open curve with multiple endpoints*/ 36 if (mode % 2) /*odd mode makes first point double*/ 37 plotline(*xp0,*yp0,0.5*(*xp0+*(xp0+2)),0.5*(*yp0+*(yp0+2))); 38 } 39 xp += 2; 40 yp += 2; 41 for (i = 1; i < (n - 1); i++, xp += 2, yp += 2) { 42 xa = 0.5 * (*(xp - 2) + *xp); 43 xc = 0.5 * ( *xp + *(xp + 2)); 44 ya = 0.5 * (*(yp - 2) + *yp); 45 yc = 0.5 * ( *yp + *(yp + 2)); 46 parabola(xa, ya, xc, yc, *xp, *yp); 47 } 48 if(mode >= 2 && mode != 4) 49 plotline(0.5*(*(xpe-2)+*xpe),0.5*(*(ype-2)+*ype),*xpe,*ype); 50 } 51 }